Understanding refrigerants in commercial heat pumps
Jason Allen of Ideal Heating Commercial looks at the importance of refrigeration choice in heat pump selection.
For those of us working systems, the heat pump has become central to the journey towards low carbon buildings. But beneath every efficient heat pump system lies an unsung hero: the refrigerant. It’s not just about selecting a heat pump anymore – it’s about choosing the right refrigerant for the right application. This is especially critical for professionals aiming to deliver sustainable, regulation-compliant solutions.
The role of the refrigerant
At its core, a heat pump transfers heat from one place to another using a refrigerant cycle. It’s the refrigerant that absorbs heat from the source (air, water or ground) and releases it into the heating system. So, the performance, environmental impact, and even the cost of running the system can hinge on which refrigerant is chosen.
Historically, refrigerants like CFCs and HCFCs were widely used, but their high ozone depletion potential (ODP) and global warming potential (GWP) led to their phase-out. This leaves us today with two main categories:
• Synthetic refrigerants – such as R32 (difluoromethane)
• Natural refrigerants – such as R290 (propane) and R744 (CO2)
Each has advantages and drawbacks, which must be understood in context.
Understanding GWP and legislation
GWP is the benchmark for assessing a refrigerant’s climate impact, comparing it to CO2 over 100 years. The lower the GWP, the lower the contribution to climate change.
The 2014 F Gas Regulations – and more recently, the EU’s Regulation 2024/573 – are pushing for a refrigerant phase-down, promoting the use of low GWP alternatives. Compliance with these regulations isn’t optional. Even though some commitments, like TM44 assessments, remain underused or misunderstood, they should be considered best practice.
Synthetic option: R32
R32 is a popular choice for commercial air source heat pumps. With a GWP of around 675, it’s significantly lower than its predecessors. One of the common misconceptions we hear is that R32 can’t produce high enough temperatures for UK heating demands. That’s simply not true. Most R32 systems can reliably produce flow temperatures up to 55°C, making them suitable for both space heating and hot water, provided the system is well designed.
Designing for R32 requires a narrow differential temperature (DT) approach and careful control of return water temperatures. But when these parameters are met, the result is a highly efficient and cost effective system.
Natural alternatives: R290 and CO2
Natural refrigerants are attracting more attention, and for good reason. R290 (propane) and R744 (CO2) boast ultra-low GWP values – just 3 for R290 and 1 for CO2. This makes them highly attractive from a sustainability standpoint.
R290 can deliver temperatures up to 75°C, making it a strong candidate for domestic hot water production and high-demand commercial systems. However, R290 is flammable, which means safety considerations and risk assessments must be built into the design and installation process.
CO2 (R744) heat pumps are especially efficient when operating in a 65–70°C flow/30°C return temperature range. They’re capable of accepting slightly higher return temperatures (up to 37°C temporarily), making them adaptable to more varied applications. However, CO2 systems require precise design due to their high operating pressures and unique transcritical cycle.
Performance metrics: COP and SCOP
Two key indicators of heat pump performance are the Coefficient of Performance (COP) and its seasonal variant, SCOP. COP is the ratio of heat output to electrical input at a specific condition, while SCOP accounts for variations over an entire year.
Natural refrigerants like CO2 can show high SCOP values in suitable applications, particularly in domestic hot water systems. However, achieving optimal SCOP means marrying refrigerant choice with building design, control strategy and realistic expectations around flow temperatures.
Designing for efficiency
No matter the refrigerant, successful heat pump design demands an integrated approach. This includes:
• Understanding the heating demand profile
• Designing with a low return temperature in mind
• Implementing variable flow control strategies
• Educating clients about realistic operating conditions
Contrary to popular belief, a heat pump doesn’t need to match the flow temperature of a gas boiler. Instead, the system should be optimised around what a heat pump can do efficiently. High-temperature outputs are possible – but not always necessary.
Cost, compliance and the future
While refrigerant type can influence system cost, natural options like R290 and CO2 are becoming increasingly viable as technology improves and demand grows. Still, system cost isn’t just about the unit – it includes installation, maintenance, training and compliance with safety standards.
It’s also important to consider refrigerant toxicity, flammability and pressure ratings. For example, while R32 and R290 have some flammability concerns, CO2 systems operate under high pressure, requiring specialised components.
Final thoughts
As installers, engineers and consultants, we all have a role in supporting the UK’s decarbonisation goals. Understanding refrigerants isn’t just a technical necessity – it’s a professional responsibility. Whether you’re specifying a new commercial plant room or retrofitting an older building, your choice of refrigerant can make or break the system’s performance, environmental impact and long-term viability.
With evolving regulations and growing emphasis on whole-system efficiency, now is the time to brush up on refrigerant knowledge and explore the full potential of heat pumps in commercial settings.
